<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <link rel="stylesheet" href="css/style.css">
    <link rel="stylesheet" href="css/style680.css" media="screen and (max-width: 680px)">
    <style>
        div:nth-child(1) {
            background: pink;
        }
        
        div:nth-child(2) {
            background: skyblue;
        }
    </style>

</head>

<body>
    <div>1</div>
    <div>2</div>
</body>

</html>